Main station and substation in a network and a method for transmitting data in a network

ABSTRACT

A method for allocating a device address in a network to a substation connected by a point-to-point connection includes transmitting an initialization message from a main station to a substation, which message contains a part of the device address, determining a set communication address of the substation, generating a complete device address based on a received part of the device address and based on the communication address, and transmitting a response mesasge from a device to the main station, which response message contains an address selected from the group consisting of the communication address, the device address, and both.

BACKGROUND OF THE INVENTION

The present invention relates to a method for allocating a deviceaddress to a substation in a network by means of a main station. Thepresent invention also relates to a substation and a main station for anetwork such as a field bus network in automation engineering.

Usually, substations in a network have fixed, unique device addressesthat permit each substation to be uniquely addressed. The deviceaddresses are generally referred to as MAC addresses and are embeddedinto the hardware of the substation. In an initialization phase of thenetwork, the device addresses of the individual substations arecommunicated to the main station so that the main station is able toselectively communicate with the individual substations of the network.Also during the initialization phase, the substations in the network areassigned IP addresses, which are either set manually or allocated by theDHCP.

Usually, however, the IP addresses must be determined and input and eachsubstation must be associated with an IP address after theinitialization phase if a user is to be able to selectively communicatewith the substation. This has the disadvantage that without consultingthe allocation information in the main station, the user does not knowthe IP address or the device address of the substation in the networkand therefore cannot perform a selective addressing.

For real-time communication, usually each of the substations in thenetwork is allocated a communication address that permits the device tobe addressed directly in a real-time channel.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a method forallocating a device address.

Another object of the present invention is to provide a substation for anetwork whose device address is automatically allocated.

A first aspect of the present invention provides a method for allocatinga device address to a substation in a network. The substation in thenetwork is connected by means of a point-to-point connection. The methodincludes the steps of transmitting an initialization message from a mainstation to the substation, where the initialization message contains apart of a device address; determining a set communication address of thesubstation for the real-time communication; generating the completedevice addresses with the aid of the received part of the device addressand with the aid of the communication address; and transmitting theresponse message from the substation to the main station, which messagecontains the communication address and/or device address.

The goal of the method according to the present invention is to allocatea device address to the substation and to announce the device address toboth the substation and the main station. Basically, the device addresscan be freely selected from within a predetermined range, but is set sothat a user who knows the part of the device address and knows thesettable communication address is able to determine the device address.Thus, for example, the device address contains several bytes, a part ofwhich is known to the user. In addition, the communication address forthe real-time communication can be set, for example manually, in thesubstation so that the part of the device address that is known to theuser and the likewise known communication address together constitutethe complete device address of the substation. This eliminates the needfor a user to first access the main station, which contains a list thatassociates the physical substations with the device addresses, in orderto find a device address that is appropriate for a particularsubstation.

Particularly in connection with the Ethernet network standard (protocol,network topology, and network hardware), known networks include switchednetworks (switched Ethernet) and networks with amplifiers (repeaters); anetwork with switched Ethernet technology is also referred to as aswitched network. The present invention can be used for all types ofsuch networks, i.e. for switched and/or unswitched networks withrepeaters, even ones based on the Ethernet standard.

According to another embodiment form of the present invention, theinitialization message can also contain a part of an IP address. Thecomplete IP address of the substation is generated with the aid of thereceived part of the IP address and with the aid of the communicationaddress. The substation transmits the response message containing thecommunication address and/or the complete IP address to the mainstation. Consequently, the complete IP address can be generated based onthe part of the IP address and the set communication address, either inthe main station or in the substation. The essential thing is that afterthe method according to the present invention has been executed, the IPaddress is present in both the main station and the substation so thatan IP communication can occur in an IP communication channel.

Alternatively, the generation of the complete IP address of thesubstation can be generated in the main station with the aid of apredetermined part of an IP address and with the aid of the transmittedcommunication address, whereupon the main station sends the device anacknowledgment message containing the complete IP address as a responseto the reception of the response message.

Another aspect of the present invention provides a substation for anetwork. The substation has a reception unit for receiving aninitialization message from a main station. A device number preparationunit supplies a communication address of the substation. In addition, acontrol unit is provided to determine a part of a device address basedon the initialization message and to generate the complete deviceaddress based on the communication address and the received part of thedevice address. A transmission unit transmits a response messagecontaining the device address and/or the communication address. Thismakes it possible to produce a substation for a network that determinesthe device address with the aid of a set or settable communicationaddress. The device address is generated inside the substation and isthen transmitted to the main station in the response message by thetransmission unit.

According to another embodiment form of the present invention, thecontrol unit can once again determine a part of an IP address based onthe initialization message and can generate the complete IP address withthe aid of the communication address and the received part of the IPaddress. The transmission unit is designed to send the response message,which contains the communication address and/or the complete IP address,depending on whether the complete IP address is to be generated by thesubstation or by the main station. If the response message contains onlythe communication address, then the reception unit can be designed toreceive an acknowledgment message containing the complete IP address asa response to the transmitted response message.

Another aspect of the present invention provides a main station for anetwork, which has a control unit for supplying a part of a deviceaddress. The main station also has a transmission unit for sending aninitialization message that contains the part of the device address. Areception unit is also provided in order to receive a response messagecontaining a communication address and/or a complete device address.

According to another embodiment form of the present invention, thecontrol unit can trigger the transmission unit to provide theinitialization message with a part of an IP address. The reception unitis also designed to receive an acknowledgment message containing thecomplete IP address as a response to the reception of the responsemessage.

The novel features which are considered as characteristic for thepresent invention are set forth in particular in the appended claims.the invention itself, however, both as to its construction and itsmethod of operation, together with additional objects and advantagesthereof, will be best understood from the following description ofspecific embodiments when read in connection with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a possible network topology of a network, according to thepresent invention,

FIG. 2 shows a block circuit diagram of a substation for the networkaccording to FIG. 1 according to the present invention,

FIG. 3 shows a block circuit diagram of a main station for a networkaccording to FIG. 1 according to the present invention,

FIG. 4 is a flowchart illustrating the method according to the presentinvention for automatically supplying a device address in a substationin a network according to FIG. 1 according to the present invention, and

FIG. 5 is a flowchart illustrating the method according to the presentinvention for automatically supplying a device address, according toanother embodiment form according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a ring network that has a main station 1 and severalsubstations 2. Each substation 2 has a data input and, separate fromthis, a data output, which can be connected to each other via arepeater. Two communication channels are provided in the networkconnections that connect the network subscribers to one another. In afirst communication channel, the real-time communication channel, themain station 1 sends data packets. A first data packet contains data forthe substations 2. The data packet also contains defined time windowsthat are each associated with one of the substations 2.

The substations 2 read the data in the defined time windows from thedata packet. The main station 1 also sends a second data packet in thereal-time communication channel, which data packet likewise has timewindows that function as placeholders for data. The data to be sent areinserted into the time window associated with the respective substation2 and the data packet thus altered is then forwarded with the inserteddata to the next network subscriber. The last substation 2 then sendsthe second data packet back to the main station 1. The second datapacket is currently filled with the data that the substations 2 havesent to the main station.

During the active phase of another communication channel, an IPcommunication channel, each of the network subscribers, i.e. the mainstation 1 and the substations 2, can transmit a data packet if no datapacket is currently present at its respective data input. In otherwords, as soon as the network is not being used, one of the networksubscribers can transmit a data packet in order to convey data. Thereal-time communication channel and the IP communication channel areconstituted by two time domains during which the correspondingcommunication channel is occupied and which follow each other incyclical sequence.

To enable communication in the real-time communication channel, eachsubstation 2 of the network is allocated a communication address. Thecommunication address is manually set or preset in each of thesubstations 2. A communication address of this kind can, for example, bea number between 1 and 254 and can thus be expressed in the form of abyte.

For the IP communication channel, each of the substations 2 must beallocated a device address. The device address is a so-called MACaddress (media access control) that is several bytes long. Inconventional IP communication devices, a device address of this kind isusually embedded in the hardware and is unique for each IP communicationdevice available on the market. In the field bus data network depictedhere, the substations 2 must each be allocated a device address. If thesubstation 2 is to also to be capable of transmitting data in the IPcommunication channel, then the substation 2 must also be allocated anIP address.

As shown in FIG. 2, a substation 2 of this kind has a reception circuit3 that is connected to a data input E and can receive data via thenetwork. A transmission unit 4 is also provided for transmitting data onthe network to a subsequent network station via a data output A. Thesubstation 2 also has a control unit 5 for operating the differentcommunication channels. Between the reception unit 3 and thetransmission unit 4, a repeater 8 is provided, which transmits data thatis present at the data input to the data output while the IPcommunication channel is active.

In the real-time communication channel, the repeater 8 is likewiseswitched to forward a data packet from the reception unit 3 to thetransmission unit 4, but is also able to extract data from acorresponding data packet and supply it to the control unit 5 and isable to insert data from the control unit 5 into a data packet to beforwarded. For the initialization during an initialization phase, thesubstation 2 awaits reception of an initialization message that isforwarded from the reception unit 3 to an initialization unit 6.

In the initialization unit 6, a part of a device address is determinedbased on the received message and this part of the device address andthe set communication address supplied by a communication addresspreparation unit 7 are combined with each other to form a completedevice address. The complete device address can, for example, beproduced by simply joining the part of the device address to themanually set communication address. There are also other conceivableways to combine the part of the device address with the communicationaddress, but it is advantageous if a user understands the combination inorder to be able to easily determine the complete device address simplyby knowing the communication address.

The initialization unit 6 transmits the complete device address to thenetwork via the reception unit 4 in the form of a response message sothat the main station 1 is informed of the device address associatedwith the respective substation 2.

In the same way, the initialization message can contain a part of an IPaddress, which the initialization unit 6 attaches to the communicationaddress for real-time communication in order to form a complete IPaddress that is unique. The complete IP address is likewise transmittedin the response message to the main station 1 via the reception unit 4so that there is a fixed association in the main station 1 between thecomplete IP address and the respective substation 2.

In an alternative embodiment form, the initialization unit 6 transmitsthe communication address supplied by the communication addresspreparation unit 7 directly to the main station 1 via the reception unit4. In this case, it is also not necessary for the initialization messageto contain the part of the device address. As soon as the main station 1receives the communication address, the main station determines thecomplete device address according to a fixed method and determines thecomplete IP address based on the preset parts of the device address andIP address and based on the communication address that has beencommunicated to it and transmits this device address to the respectivesubstation 2 in an acknowledgment message.

FIG. 3 shows an embodiment form of a main station. The main station 10has a reception unit 11 and a transmission unit 12 that are connected tothe substations 2 via appropriate network lines. The main station 10also has an initialization unit 13 which, triggered by a control unit15, generates an initialization message and transmits it via thetransmission unit 12. The initialization message contains a part of adevice address that is received from one of the substations 2 and, withthe aid of the communication address set therein, can be processed toproduce a complete device address.

The reception unit 11 of the main station 10 receives the completedevice address in the form of a response message, thus enabling anassociation between the complete device address and the respectivesubstation to be stored in a memory 14 of the main station. In the samemanner, the initialization message can also contain a part of an IPaddress that is completed in the substation and sent back to the mainstation 10 via the response message. Alternatively, the main station 10can also receive the complete device address in the response message,generate the complete IP address based on it, and transmit anacknowledgment message to the respective substation 2 via thetransmission unit 12 so that the substation also contains the unique IPaddress associated with it.

FIG. 4 is a flowchart illustrating the method according to the presentinvention. The method relates to the initialization and allocation ofdevice addresses and IP addresses in a network, e.g. in a field busnetwork for automation engineering. For the initialization, the mainstation transmits an initialization message that contains a part of adevice address and/or a part of an IP address, which message is receivedby a substation. The substation first determines the set communicationaddress for real-time communication and based on it, generates thecomplete device address and the complete IP address. Then the substationsends the main station a response message containing the complete deviceaddress and the complete IP address. As a result, the complete deviceaddress and complete IP address are present in both the substation andthe main station so that the main station contains an associationbetween the relevant substations and the complete device address andcomplete IP address.

FIG. 5 shows an alternative method. In it, the main station sends theinitialization message, thus prompting the substation to determine thecommunication address contained therein and to send it in a responsemessage to the main station. Then the complete device address andcomplete IP address are generated in the main station based on the partof the device address contained therein and part of an IP address andbased on the communication address that has been sent to it and then anacknowledgment message containing the complete device address andcomplete IP address is sent to the respective substation.

According to another embodiment form of the present invention, insteadof the communication address, an IP address can be preset, e.g. setmanually, and the communication address for the real-time communicationcan be derived from this. In this case, the communication address wouldcorrespond to an IP address and the complete IP address would bedetermined based on the fixed, predetermined IP address.

If, for example, were set as a communication address in the real-timecommunication channel 5, then in an example, the device address and theIP address as well would end with 5, e.g. an IP address of 192.168.0.5.The main station would consequently transmit the first three bytes ofthe IP address along with the initialization message to the substation,thus permitting 255 different IP addresses to be allocated.

It is also optionally possible for there to be an agreement regarding atimeout of the addresses so that even while a substation is operating,its acquired portion of the address can be changed.

Alternatively, the initialization method according to the presentinvention can be used to allocate a device address and an IP address toeach of the substations 2 of the above-described data network; it isalso possible, however, for the device address and the IP address to bepreset, e.g. with the aid of an input unit into which these addressescan be input.

If agreements have been established in the data network regardingnormally reserved IP addresses, then it is also possible for thesubstation to check whether the main station has the same IP address asit does itself. If the substation determines that the main station hasthe same IP address, then the substation uses a new IP address takenfrom the reserved range.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions and methods differing from the types described above.

While the invention has been illustrated and described as embodied in amethod for allocating a device address to a substation in a network aswell as a substation and a main station for a network, it is notintended to be limited to the details shown, since various modificationsand structural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will reveal fully revela thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic or specific aspects of theinvention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.

1. A method for allocating a device address in a network to a substationconnected by a point-to-point connection, the method comprising thesteps of transmitting an initialization message from a main station to asubstation, which message contains a part of the device address;determining a set communication address of the substation; generating acomplete device address based on a received part of the device addressand based on the communication address; and transmitting a responsemesasge from a device to the main station, which response messagecontains an address selected from the group consisting of thecommunication address, the device address, and both.
 2. A method asdefined in claim 1, wherein said transmissitting the initializationmessage includes transmitting such initialization message which alsocontains a part of an IP address; and further comprising generating acomplete IP address of the substation via a received part of the IPaddress and with the aid of the communication address; and transmittingfrom the substation to the main station the response message whichcontains the address selected from the group consisting of thecommunication address, the complete IP address, and both.
 3. A method asdefined in claim 1; and further comprising generating in the mainstation a complete IP address of the substation with the aid of a presetpart of an IP address, and the transmitting communicated address; andtransmitting to the substation an acknowledgement message containing thecomplete IP address as a response to a reception of the responsemessage.
 4. A substation for a network, comprising a reception unit forreceiving an initialization message from a main station; a communicationaddress preparation unit for producing a communication address of thesubstation; a control unit for determining a part of a device addressbased on the initialization message, for generating a complete deviceaddress based on a received part of the device address and based on thecommunication address; and a transmission unit for transmitting aresponse message containing an address selected from the groupconsisting of the device address, the communication address, and both.5. A substation as defined in claim 4, wherein said control unit isformed so as to determine also a part of an IP address based on theinitialization message and to generate a complete IP address with theaid of a received part of the IP address and with the aid of thecommunication address, said transmitting unit being configured so as totransmit the response message that contians the address selected fromthe group consisting of the communication address, the complete IPaddress and both.
 6. A substation as defined in claim 5, wherein saidreception unit is also configured so as to receive an acknowledgementmessage containing the complete IP address as a response to thetransmitted response message.
 7. A main station for a network,comprising a control unit for controlling a network communication and anIP communication channel in order to supply a part of a device address;a transmission unit for transmitting an initialization message whichcontains the part of the device address; and the reception unit forreceiving a response message via an IP communication channel, whichmessage contains an address selected from the group consisting of acommunication address, a complete device address, and both.
 8. A mainstation as defined in claim 7, wherein said control unit is configuredso as to trigger the transmission unit to provide the initializationmessage with a part of an IP address, while said reception unit isconfigured so as to receive an acknowledgement message containing acomplete IP address as a response to a reception of the responsemessage.